A. Technical Field
The present invention relates to: a production process for a polymer, particularly, a production process preferably applied to the production of a water-soluble polymer; and a production apparatus therefor.
B. Background Art
Polymers such as a water-soluble polymer, particularly, acrylic acid polymer having many carboxylic groups, maleic acid polymers copolymers thereof, and these polymers into which a sulfonic group or a hydroxyl group was further introduced, are well-known to be able to display superior calcium-ion-binding capability and clay-dispersing functions, and superior anti-gelation capability. Therefore, these polymers are used in the very wide range, for example, for inorganic pigment dispersants, scale inhibitors, chelating agents, detergent compositions, fiber-treating agents, wood pulp-bleaching assistants.
Many studies and developments as to production processes for these polymer have been carried out up to this day, and are disclosed in, for example, JP-A-270605/1987, JP-A-239114/1993, JP-A-247143/1993, JP-B-2167/1991, JP-B-14046/1991 and Japanese Patent No. 2574144.
These prior studies and developments aimed at, for example, adjusting components and molecular weight, and decreasing the amount of residual monomer in order to making the best use of characteristics of the water-soluble polymers and so on, and to answer the above various use.
However a scale-up problem as to production processes for these polymers has not been considered up to this day. When a production process having 100 g to about 5 kg scale in the stage of a laboratory is turned into a practical plant having very large 1 to 30 t scale, it is inevitable to solve a problem of removing heat. In general, it is said that: the larger scale a production process is, the worse an ability for removing heat becomes like an exponential decrease from the relationship between surface area and volume of a polymerization reactor.
In view of safety and economy, it is general to produce a polymer in an aqueous solvent and at a high temperature, if possible, at a temperature in the vicinity of the boiling point. Therefore, decrease of ability for removing heat results in foaming extremely, namely, extremely boiling state, and losing stirring effect. At last, a problem that the reaction solution overflows the polymerization reactor and the polymerization itself cannot be continued, is caused. In recent years, a concentration of raw materials tends to rise in view of improving productive efficiency, still more, the decrease has resulted in foaming extremely, namely, extremely boiling state easily.
In order to suppress such as foaming and boiling phenomenon, a condenser so that a vaporized reaction solution by boiling can be cooled and returned to the reactor, is placed generally as a portion of a production apparatus. However if a foaming state becomes violent beyond cooling ability of the condenser, a reflux amount, namely, a vapor velocity becomes very large, the foaming cannot be suppressed, the polymerization itself cannot be continued, and decrease of productivity such as attaching gel in the polymerization reactor is caused. In addition, a problem that a distribution of a weight molecular weight of the obtained polymer becomes broad, is caused. On the other hand, if heat quantity of the polymerization reactor is lacking, it is difficult to arise foaming and boiling phenomenon. However if the vapor velocity is too low, a problem that a distribution of a weight molecular weight of the obtained polymer becomes broad and reproducibility of the obtained polymer becomes much lower, is caused.
The problem like this can be solved by prospecting foaming state at producing the polymer beforehand precisely, and adjusting cooling ability of the condenser and heating condition of the polymerization reactor. However it is difficult to prospect the foaming state at producing the polymer beforehand precisely because the state is different owing to various conditions such as polymerization system and the polymerization reactor.
A. Object of the Invention
An object of the present invention is to provide: a production process that enables to keep foaming state within a constant level and to obtain a polymer with good productivity and reproducibility with a practical plant by defining an appropriate vapor velocity from a weight-average molecular weight of the polymer that is finally intended to obtain; and a polymerization apparatus therefor.
B. Disclosure of the Invention
The present inventors diligently studied to solve problems of foaming that is caused when producing a polymer with a level of the practical plant and in a high concentration and a short time. As a result, they hit on an idea that: foaming state can be kept within a constant level and physical properties of the obtained polymer can be controlled by defining precisely an appropriate vapor velocity allowed for a weight-average molecular weight of the polymer that is intended to obtain, and completed the present invention.
Accordingly, a production process for a polymer, according to the present invention, comprises the steps of: refluxing and cooling a vapor generated in a reaction, and returning the vapor to the reaction system in order to produce the polymer, wherein the vapor velocity is adjusted in the range of 0.001 to 0.05 m/s so that a common logarithm value of a weight-average molecular weight of the polymer that is finally intended to obtain multiplied by the value of the vapor velocity can be not more than 0.15 for not less than 10% of the whole reaction time.
In addition, a production apparatus for producing a polymer, according to the present invention, comprises a reactor in order to produce the polymer, a stirrer in order to stir a reaction solution in the reactor, and a condenser so that a vaporized reaction solution can be cooled and returned to the reactor, with the production apparatus further comprising a vapor velocity measuring means of monitoring a vapor velocity in the condenser, and an vapor velocity adjusting means of adjusting the vapor velocity.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.